How is a prediction market fee calculated?

Both Kalshi and Polymarket use a version of fee = round up (0.07 × contracts × price × (1 − price)), where price is between $0.01 and $0.99. The fee peaks at a 50-cent contract price (the most balanced market) and shrinks toward near-zero at extreme prices close to $0.01 or $0.99.

What's the difference between a maker and a taker fee?

A taker order fills immediately against an existing order and pays the standard fee. A maker order rests on the book waiting to be matched and costs substantially less — roughly a quarter of the taker rate on Kalshi, and zero (with a rebate) on Polymarket — in exchange for the risk the order never fills.

Are there costs beyond the per-trade fee on Kalshi and Polymarket?

Yes. Kalshi charges an extra 2% on debit card deposits (ACH transfers are typically free), and Polymarket, built on the Polygon network, adds small gas fees per transaction plus potentially larger bridge fees if moving funds back to Ethereum mainnet.

Prediction market fees explained (maker vs taker on Kalshi and Polymarket)

Last updated: 2026-07-29 · Written by Elena Kovač

Kalshi is a CFTC-regulated US exchange, and Polymarket is a crypto-based platform built on the Polygon network — both let traders buy and sell contracts tied to a real-world outcome, priced between $0.01 and $0.99, with each contract settling at $1 if the outcome happens. Neither charges a flat percentage commission the way a sportsbook builds vig into its odds. Instead, both use a fee formula tied to how close the contract price sits to an even 50/50, and both charge less — or nothing — for orders that add liquidity to the market instead of taking it.

The fee formula, and why it peaks at 50 cents

Both platforms use a version of the same formula: fee = round up (0.07 × contracts × price × (1 − price)), with price expressed as a fraction between $0.01 and $0.99. That formula is parabolic — it peaks at the most balanced price point, 50 cents, where a contract carries the maximum possible fee of about $0.0175 per contract, and drops toward close to zero at extreme prices near $0.01 or $0.99. A near-certain outcome priced at 95 cents costs far less in fees than a genuine coin-flip market priced at 50 cents, because the fee is built around the market's own uncertainty, not a flat cut of the trade.

Maker vs taker: why the order type changes the cost

A taker order fills immediately against an existing order already sitting on the book — that's the standard fee described above. A maker order rests on the book waiting for someone else to trade against it instead of filling right away, and both platforms charge makers substantially less: Kalshi maker fees run roughly a quarter of the taker rate, while Polymarket makers pay zero fees and instead earn a rebate — about 20% of the taker fees collected on the trades that fill against their resting orders. The trade-off is patience: a maker order might not fill at all if the price never reaches it, while a taker order fills instantly at a worse price.

Deposit, withdrawal, and network costs beyond the trading fee

Kalshi funds via bank transfer (ACH, typically free) or debit card, where card deposits carry an additional 2% fee that should be factored into cost basis before funding that way rather than via ACH; withdrawals are generally free. Polymarket runs on the Polygon network and charges nothing itself to deposit or withdraw USDC, but every on-chain transaction — placing a trade, moving funds — carries a small Polygon gas fee, typically a few cents, and bridging funds back to Ethereum mainnet (rather than staying on Polygon) can cost several dollars in bridge fees. Neither of these network or funding costs shows up in the headline trading fee, but both add up for anyone trading frequently.

How this differs from a sportsbook's vig

A sportsbook builds its edge into the odds themselves before you ever place a bet — see prediction markets vs sportsbooks explained for how that structural difference plays out more broadly. A prediction market instead prices trades transparently, with the fee itself visible and calculable per trade rather than baked invisibly into a shaded price, and traders set the price against each other rather than an operator setting it unilaterally. That transparency doesn't mean trading is free — the maker/taker structure and peaked fee curve still add up, especially on close-to-even markets traded frequently — but it means the cost is a known, calculable number rather than an implicit one.

Payment speed doesn't change the maths of gambling — only bet what you can afford to lose; gambling should be entertainment, never a way to make money. Set limits and get help here.

FAQ

How is a prediction market fee calculated? Both Kalshi and Polymarket use a version of fee = round up (0.07 × contracts × price × (1 − price)), where price is between $0.01 and $0.99. The fee peaks at a 50-cent contract price (the most balanced market) and shrinks toward near-zero at extreme prices close to $0.01 or $0.99.
What's the difference between a maker and a taker fee? A taker order fills immediately against an existing order and pays the standard fee. A maker order rests on the book waiting to be matched and costs substantially less — roughly a quarter of the taker rate on Kalshi, and zero (with a rebate) on Polymarket — in exchange for the risk the order never fills.
Are there costs beyond the per-trade fee on Kalshi and Polymarket? Yes. Kalshi charges an extra 2% on debit card deposits (ACH transfers are typically free), and Polymarket, built on the Polygon network, adds small gas fees per transaction plus potentially larger bridge fees if moving funds back to Ethereum mainnet.

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